Clinical studies with mitoxantrone and clodronate showed a better pain reduction in patients with prostate cancer. Both in vitro and animal studies have shown that paclitaxel and biphosphonates act synergistically and prevent formation and progression of bone metastasis (breast cancer). This clinical trial studies the effect of risedronate and docetaxel in the treatment of hormone refractory prostate cancer.

Treatment will be given until progression, or 10 courses. After progression Risedronate 30 mg od + prednisone 5 mg will be continued.

- Primary outcome

The primary objective of phase II part is to assess the objective PSA response to treatment by serial measurements of serum PSA as defined by the "Bubley".
Primary objectives phase III study is to compare time to progression between concomitant and sequential use of docetaxel and risedronate, in combination with prednison.